Don't build broken Haskell packages on Hydra.

These packages don't compile:

 - cabal-delete
 - cabal-file-th
 - categories
 - cmdtheline
 - codec-image-devil
 - concurrent-extra
 - cryptol 1.8.x
 - data-lens
 - diagrams-postscript
 - djinn
 - download
 - dstring
 - enummapset
 - git-date
 - github-backup
 - gtkglext
 - happyy-meta
 - haskeline-class
 - pakcs

These packages depend on some of the packages listed before:

 - data-lens-template
 - purescript

These packages fail with GHC 7.8.3 but still compile with older compilers:

 - happy: 1.18.4, 1.18.5, 1.18.6